1. Field of the Invention
This invention relates to a color liquid crystal display device, more particularly to a color liquid crystal display device capable of high color reproduction.
2. Description of the Related Art
Recently, liquid crystal display devices have been increasingly developed due to their characteristics, such as light weight, thin profile, and power saving, in the application of notebook computers and digital cameras. Generally, the color liquid crystal display devices for desktop computers have color reproduction ranging from about 50% to about 60% of NTSC (National Television Standards Committee) color gamut. The color reproduction of liquid crystal display television ranges from about 60% to about 75%. There is a need for a relatively broad range of color reproduction in the art.
A liquid crystal display device is generally configured with a trichrome backlight unit and a color filter. However, a combination of a backlight unit and a color filter of the prior art cannot satisfy the requirement of the color reproduction and the color tone for the liquid crystal display television. Therefore, there are problems of a narrow range of the color reproduction and a low color temperature. Additionally, in the case of a backlight unit for a desktop computer, when it is intended to produce a color filter having chromaticity specified in EBU (European Broadcasting Union) standard, it is often required to increase the film thickness and/or the pigment concentration for blue pixels of a color filter. Therefore, the light transmittance of the blue pixels is undesirably reduced, the display properties of the liquid crystal display are deteriorated, and the color temperature of the liquid crystal display device is also undesirably reduced.
Since phthalocyanine-based blue pigments have excellent light resistance and heat resistance, they are often used in the blue pixels of a color filter. Examples of the phthalocyanine-based blue pigments include C.I. Pigment Blue 6 (C.I. PB6), C.I, Pigment Blue 15 (C.I. PB15:1, 15:2, 15:3, 15:4, 15:5, and 15:6), C.I. Pigment Blue 21 (C.I. PB21), C.I. Pigment Blue 22 (C.I. PB22), C.I. Pigment Blue 28 (C.I. PB28), C.I. Pigment Blue 60 (C.I. PB60), and C.I. Pigment Blue 64 (C.I. PB64). Furthermore, violet pigments are used for adjusting the chromaticity of the blue pigments. Examples of the violet pigments include C.I. Pigment Violet 14 (C.I. PV14), C.I. Pigment Violet 19 (C.I. PV19), C.I. Pigment Violet 23 (C.I. PV23), C.I. Pigment Violet 29 (C. I. PV29), C. I. Pigment Violet 32 (C. I. PV32), C.I. Pigment Violet 33 (C.I. PV33), C.I. Pigment Violet 36 (C.I. PV36), C.I. Pigment Violet 37 (C.I. PV37), C.I. Pigment Violet 38 (C.I. PV38), C.I. Pigment Violet 40 (C.I. PV40), and C.I. Pigment Violet 50 (C.I. PV50).
JP 09-095638 discloses a blue pigment composition for a color filter, which comprises alpha-copper phthalocyanine blue pigment and epsilon-copper phthalocyanine blue pigment.
JP 09-197663 discloses another blue pigment composition for a color filter, which comprises copper phthalocyanine blue pigment and indanthrone blue pigment.
The blue pixels made of the blue pigments as described above have relatively low light transmittance. Therefore, there is a problem of insufficient light transmittance when the blue pixels are used to produce a color filter required for superior color reproduction. A color liquid crystal display having high definition cannot be provided thereby. Additionally, a color liquid crystal display having a satisfactory broad range of color reproduction cannot be obtained from a combination of the aforesaid color filter made of the blue pigments with a light source of the prior art.
Therefore, it is still required in the art to provide a color liquid crystal display device having high color reproduction.